They're offshore knockoffs that sorta-kinda resemble the original carbs. They'll make most engines run, but not even close to correctly, compared to an original equipment carb. Unless the castings have big holes rotted into them, that cruddy OEM carb can probably be rebuilt to perform much better than a new "clone" that looks better than it runs.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!